This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. It is very likely that the continuing epidemic spread of 2009 H1N1 Influenza A virus infection in the US will greatly increase in the fall-winter season when social interactions and climactic conditions become even more conducive to spread of influenza viruses. While reports to date suggest that healthy individuals typically have a mild illness, underlying medical conditions including immunodeficiency appear to increase risk for severe disease and even death with pandemic H1N1. Thus, knowledge of the immunogenicity of several of the licensed Influenza A (H1N1) 2009 Monovalent Vaccines in HIV-1 perinatally infected children and youth is critically important to address the health care needs of this vulnerable population. It is well established that seasonal influenza infection impacts children in a community before becoming widespread in adult populations. Susceptibility to disease among young populations appears even more pronounced with 2009 H1N1 Influenza A virus as one third of older adults have measurable levels of serum HAI or neutralizing antibody against the 2009 H1N1 Influenza A virus while young adults and children completely lack protective titers. The serologic data is consistent with the observation that the attack rate and disease severity for the virus appears to be much higher in younger populations with relative protection of those 50 years of age. Efforts are currently underway to evaluate Influenza A (H1N1) 2009 monovalent vaccines in healthy children as well as other populations. Protection of HIV-1 perinatally infected children and youth from 2009 H1N1 Influenza A virus will require knowledge of immunogenicity of these new licensed products in this population. This study, P1089, will assess the immune response following receipt of licensed Influenza A (H1N1) 2009 monovalent vaccines in HIV-1 perinatally infected children and youth in the US and Puerto Rico. In order to understand the mechanism of disease and protection, we will investigate the short term seroresponse in this population. In summary, 2009 H1N1 Influenza A virus is likely to infect a significant proportion of HIV-1 perinatally infected children and youth. Immunogenicity of licensed available Influenza A (H1N1) 2009 monovalent vaccines must be established in HIV-1 perinatally infected children in order to assure that this population is protected. Lack of a protective immune response would support the need for additional measures to protect this high risk population.